package com.wc.alorithm_blue_bridge._前缀和与差分.守护射手座;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.util.StringTokenizer;

/**
 * @Author congge
 * @Date 2025/5/24 19:08
 * @description
 * https://www.lanqiao.cn/problems/20318/learning/?contest_id=255
 */
public class Main {
    /**
     * 思路：
     * 只要不够就合并, 够了就新开, 最后一个不够就和前面合并, 整体不够就-1
     */
    static FastReader sc = new FastReader();
    static PrintWriter out = new PrintWriter(System.out);
    static int N = 100010;
    static int[] a = new int[N];
    static int n, m;

    public static void main(String[] args) {
        n = sc.nextInt();
        m = sc.nextInt();
        for (int i = 1; i <= n; i++) a[i] = sc.nextInt();
        int sum = 0, lid = 0;
        int res = 0;
        for (int i = 1; i <= n; i++) {
            if (sum + a[i] >= m) {
                res += i - lid - 1;
                lid = i;
                sum = 0;
            } else sum += a[i];
        }
        if (sum > 0) res += n - lid;
        if (lid == 0) res = -1;
        out.println(res);
        out.flush();
    }
}

class FastReader {
    StringTokenizer st;
    BufferedReader br;

    FastReader() {
        br = new BufferedReader(new InputStreamReader(System.in));
    }

    String next() {
        while (st == null || !st.hasMoreElements()) {
            try {
                st = new StringTokenizer(br.readLine());
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
        return st.nextToken();
    }

    int nextInt() {
        return Integer.parseInt(next());
    }

    String nextLine() {
        String s = "";
        try {
            s = br.readLine();
        } catch (IOException e) {
            e.printStackTrace();
        }
        return s;
    }

    long nextLong() {
        return Long.parseLong(next());
    }

    double nextDouble() {
        return Double.parseDouble(next());
    }

    // 是否由下一个
    boolean hasNext() {
        while (st == null || !st.hasMoreTokens()) {
            try {
                String line = br.readLine();
                if (line == null)
                    return false;
                st = new StringTokenizer(line);
            } catch (IOException e) {
                throw new RuntimeException(e);
            }
        }
        return true;
    }
}

